package lyl.servlet;

import java.io.IOException;
import javax.servlet.Filter;
import javax.servlet.FilterChain;
import javax.servlet.FilterConfig;
import javax.servlet.ServletException;
import javax.servlet.ServletRequest;
import javax.servlet.ServletResponse;

/**
 * 解决网页传递参数中文问题
 * 
 * jsp页面中设置成utf-8,然后加一个这样的过滤类
 * 
 * 然后在web.xml文件中配置一下就可以了 <filter> <filter-name>Set Character Encoding</filter-name> <filter-class>com.bx.util.SetEncodingFilter类的路径</filter-class> <init-param> <param-name>encoding</param-name>
 * <param-value>UTF-8</param-value> </init-param> </filter> <filter-mapping> <filter-name>Set Character Encoding</filter-name> <url-pattern>/*</url-pattern> </filter-mapping>
 * 
 * @author Liu Yulong
 */
public class SetEncodingFilter implements Filter {

    // ----------------------------------------------------- Instance
    // Variables

    /**
     * The default character encoding to set for requests that pass through this filter.
     */
    protected String encoding = null;

    /**
     * The filter configuration object we are associated with. If this value is null, this filter instance is not currently configured.
     */
    protected FilterConfig filterConfig = null;

    /**
     * Should a character encoding specified by the client be ignored?
     */
    protected boolean ignore = true;

    // --------------------------------------------------------- Public
    // Methods

    /**
     * Take this filter out of service.
     */
    public void destroy() {

	this.encoding = null;
	this.filterConfig = null;

    }

    /**
     * Select and set (if specified) the character encoding to be used to interpret request parameters for this request.
     * 
     * @param request
     *                The servlet request we are processing
     * @param result
     *                The servlet response we are creating
     * @param chain
     *                The filter chain we are processing
     * 
     * @exception IOException
     *                    if an input/output error occurs
     * @exception ServletException
     *                    if a servlet error occurs
     */
    public void doFilter(ServletRequest request, ServletResponse response,
	    FilterChain chain) throws IOException, ServletException {

	// Conditionally select and set the character encoding to be used
	if (ignore || (request.getCharacterEncoding() == null)) {
	    String encoding = selectEncoding(request);
	    if (encoding != null) {
		request.setCharacterEncoding(encoding);
	    }
	}

	// Pass control on to the next filter
	chain.doFilter(request, response);

    }

    /**
     * Place this filter into service.
     * 
     * @param filterConfig
     *                The filter configuration object
     */
    public void init(FilterConfig filterConfig) throws ServletException {

	this.filterConfig = filterConfig;
	this.encoding = filterConfig.getInitParameter("encoding");
	String value = filterConfig.getInitParameter("ignore");
	if (value == null) {
	    this.ignore = true;
	} else if (value.equalsIgnoreCase("true")) {
	    this.ignore = true;
	} else if (value.equalsIgnoreCase("yes")) {
	    this.ignore = true;
	} else {
	    this.ignore = false;
	}

    }

    // ------------------------------------------------------ Protected
    // Methods

    /**
     * Select an appropriate character encoding to be used, based on the characteristics of the current request and/or filter initialization parameters. If no character encoding should be set, return
     * <code>null</code>.
     * <p>
     * The default implementation unconditionally returns the value configured by the <strong>encoding</strong> initialization parameter for this filter.
     * 
     * @param request
     *                The servlet request we are processing
     */
    protected String selectEncoding(ServletRequest request) {

	return (this.encoding);

    }

}